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[gentle music]

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>> Since about the start of
 the Industrial Revolution,

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we've seen CO2 levels

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in the atmosphere
 increase by about 30%.

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Human activity is causing
  a tipping of the scales,

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this very fine delicate
balance that we have

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and what we call the
 carbon cycle here.

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>> The key motivation
for the OCO-3 experiment

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is to continue this
  record of carbon dioxide.

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OCO-2 was built
  to last two years.

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We've had it up
 there for four years,

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but there's always a risk
  it's not gonna survive,

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so OCO-3 goes on the space
  station in the spring.

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[gentle music]

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We'd like to have measurements
 that cover a long duration,

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and OCO-3 is gonna help
add to that record.

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>> OCO-3 is gonna
 specifically produce a dataset

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of carbon dioxide measurements.

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We'd like to be able to keep
an eye on this atmospheric CO2,

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where did it come
from, where's it going,

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and how is it related to
other global processes.

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>> Annmarie: When plants
  are doing photosynthesis,

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they emit a little bit of light,

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and we can sense that
  light in our measurements,

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so we have a measure of
 plant photosynthesis activity

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in combination with
 the carbon dioxide.

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>> Plants use CO2 for growing.

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They absorb it into the leaves,

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they convert CO2
 and water into sugar

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that they use to store
  the energy to grow later.

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The combination of
  these measurements

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can tell us about
  the relationship

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between this net
uptake of CO2 over time

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and how that is being
 governed by photosynthesis.

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>> OCO-2 measures every
  day, the same time of day.

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With OCO-3 on the space station,

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we're gonna sample from
sunlight to sundown,

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and so now we can learn
about carbon cycle

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through different
  parts of the day,

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and that's really important,
 because plants respond to sun,

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so we need to see them
behaving across the day.

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[gentle music]

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>> Ralph: Our team
  designed and built

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an agile, mechanical
  actuator that allows OCO-3

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to look at dozens of areas
  on the globe each day,

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and each of these areas is about

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50 miles by 50 miles in
 size, and so that allows us

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to actually focus in
 on specific areas,

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maybe urban areas, as well
  as agricultural regions.

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>> This capability
 of OCO-3 to map out

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some of those areas and start to

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see some change over time,
and that really is how

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we are gonna advance
 our understanding

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and our modeling for the future